As one kind of semiconductor devices, a NAND type flash memory device having a three-dimensional structure is known in the art. In the manufacture of the NAND type flash memory device having the three-dimensional structure, there is performed a process of forming a deep hole in a multilayered film, in which silicon oxide films and silicon nitride films are alternately stacked on top of each other, by etching the multilayered film. This etching process is described in Patent Document 1.
To be specific, in Patent Document 1, there is disclosed a method of etching a multilayered film by exposing a processing target object having a mask on the multilayered film to plasma of a processing gas.
Patent Document 1: U.S. Patent Application Publication No. 2013/0059450
A processing target object to be etched may include a first region including a multilayered film in which silicon oxide films and silicon nitride films are alternately stacked on top of each other; and a second region including a silicon oxide film having a thickness larger than a thickness of the silicon oxide film of the first region. It is required to form a space such as a hole and/or a trench in the first region and in the second region at the same time by etching the processing target object.
To etch the first region and the second region concurrently, a mask is provided on the first region and the second region, and portions of the first region and the second region exposed through openings of the mask are etched. In this etching process, plasma of a processing gas containing a fluorocarbon gas and a hydrofluorocarbon gas may be generated within a processing vessel of a plasma processing apparatus.
In the etching with the plasma of the processing gas, however, the width of a space formed in the second region may be enlarged at a portion thereof in a depth direction. That is, verticality of a sidewall surface surrounding the space formed by the etching of the second region may be deteriorated.
In this regard, in the technique of concurrently etching the first region including the multilayered film in which the silicon oxide films and the silicon nitride films are alternately stacked and the second region including the silicon oxide film having the thickness larger than the thickness of the silicon oxide film of the first region, it is required to improve the verticality of the sidewall surface formed by the etching.